WORKING MIXTURE FOR REFRIGERATION MACHINERY

Abstract: The present invention relates to refrigeration equipment, and particularly, to household refrigerators, and can be utilized in medium-temperature refrigerators, air conditioners, including vehicle and heat pumps, and for conducting researches. The blend of the invention is difluoroethane (R152a)-based refrigerant blend, further comprising isobutane (R600a). There is also proposed a range of component concentrations providing an azeotropic character of the blend, namely, from 60 to 75 weight percent of R152a and from 25 to 40 weight percent of R600. Under the proposed range of concentrations the refrigeration coefficient of the refrigerant blend according to the present invention exceeds the appropriate coefficient for R12. The blend possesses zero ozone depletion potential and the components thereof have close molecular masses.

Description: Field of the Invention The present invention relates to refrigeration equipment, and particularly, to household refrigerators, and can be utilized in medium-temperature refrigerators, air-conditioners, including vehicle and heat pumps, and for conducting researches. Background of the Invention In the art are known several trends of developing refrigerants as replacements for R12 refrigerant, not depleting ozone layer of the earth's atmosphere. One of said trends is based on utilization of hydrocarbons in a refrigerant composition. Known in the art is a refrigerant blend consisting of a mixture of chlorodifluoromethane (CHF 2 CL, R22) with isobutane (C 4 H 10 , R600a) and comprising from 65 to 80 weight percent of chlorodifluoromethane and from 20 to 35 weight percent of isobutane (GB, A, 2228739). The aforementioned refrigerant blend possesses the refrigeration capacity and energy efficiency comparing favorably with dichloro-difluoromethane (CF 2 Cl 2 , R12), but exerts less impact on the earth's ozone layer. However, said refrigerant blend is a nonazeotropic composition which reduces an efficiency of filing up a refrigerant into a refrigeration unit under the industrial scale conditions, and also complicates performance of the refrigerator when refilling is needed. Additionally, R22 refrigerant relates to a group of the so-called "transient" refrigerants and, according to the international agreements on the Earth's atmospheric ozone layer protection, its usage should be completely terminated by 2020. Known in the art are refrigerant blends based on more environmentally acceptable refrigerants than R22. Particularly, known is pentafluoroethane-based refrigerant blend (C 2 HF 5 , R125) containing isobutane R600a. This composition comprises from 60 to 80 weight percent of R125 (GB, A, 2247462). Utilization of said blend in refrigerators is complicated due to an undeveloped commercial technology of R125 refrigerant production. In addition, relatively high content of fluorine in R125 molecule (5 atoms) causes an increased consumption of fluorine to produce said refrigerant and, as a result, raises its cost. It should be noted that under temperatures inherent to refrigerator evaporators (from -20 to -25°C), said composition would have a pressure higher than a pressure of R12, which entails problems of its utilization as a substitute for of R12. Also, known in the art is a refrigerant blend consisting essentially of 1,1,2,2-tetrafluoroethane (CHF 2 CHF 2 , R134) and isobutane R600a and comprising from 70 to 99 weight percent of 1,1,2,2, tetrafluroethane and from 1 to 30 weight percent of isobutane (PCT/US 92/02136). The advantage of said refrigerant blend resides in its azeotropic nature. However, R134 refrigerant used as a base for the aforementioned composition possesses high global warming factor of 0,3 which does not entirely meet the environmental safety requirements. Also, known are compositions for refrigerators, based on 1,1-difluoroethane (CHF 2 CH 3 , R152a). Said refrigerants, similarly to R134, have zero ozone depletion potential, however, as compared to R134, they have 10 times lower global warming factor (0,03) and better oil solubility. Under the normal atmospheric pressure, difluroethane boils at -25°C and is close to R12 by its thermodynamic properties. Also, known in the art is a refrigerant blend based on 1,1-difluoroethane (R152a), additionally comprising chlorodifluoromethane (R22) at the following content of components: from 50 to 65 weight percent of 1,1-difluoroethane and from 35 to 50 weight percent of chlorodifluoromethane R22 (DD, A, 271122). Under the components ratio R22/R152a close to 40:60, said composition has an azeotropic nature and the energy characteristics there of correspond to those of R12 when it is used as a refrigerant. However, said 1,1-difluoroethane-based refrigerant blend has certain disadvantages. As mentioned above, R22 refrigerant is a transient composition and should be taken from utilization. Owing to its presence in a refrigerant composition, the blend has other than zero ozone depletion potential. Additionally, R22 is relatively poor soluble in mineral oils used for compressor lubrication which aggravates performance of the equipment. The energy efficiency of equipment filled up with said refrigerant blend can not be raised due to different molecular masses of components included thereto. Thus, molecular mass of R22 is 86.5 and that of R152a is 66.1. A mixture of said gases flowing through a constriction or a capillary, according to Fick's second law, fractionates into components at a factor proportional to M 1 /M 2 , where M 1 and M 2 are molecular masses of the components. Moreover, having passed through a constriction, the lighter component is enriched and the heavier one depleted. As a result, different concentration zones, other than the original ones, appear in a closed gas cycle. Hence, an equipment using such a blend loses stability of working parameters due to an alternating variation of the refrigerant component contents which leads to a failure of condenser operation, to unstable operation of evaporator and, ultimately, to energy consumption raise. Also known in the in the art (JP 01139677) is a refrigerator blend containing as essential components: (A) at least one hydrocarbon compound with 4-5 carbon atoms; (B) dichlorodifluoromethane; and (C) 1,1-difluoroethane. However, since such a refrigerator blend does not passes an azeotropic nature, its operational and energy characteristics will be reduced accordingly. Moreover, dichloro-difluoromethane is a chlorine containing compound that depletes the Earth's ozone layer. Summary of the Invention The object of the present invention is to provide a 1,1-difluoroethane-based refrigerant blend ensuring better ozone layer safety, increase of energy efficiency and improving a reliability of refrigerator performance. The present invention provides a reduction of ozone depletion potential of a 1,1-difluoroethane-based refrigerant blend and an increase of a refrigeration coefficient. Said object is attained by 1,1-difluoroethane-based refrigerant blend (R152a), additionally comprising isobutane (R600a). The blend of the invention comprises from 60 to 75 weight percent of 1,1-difluoroethane and from 25 to 40 weight percent of isobutane. The preferred relationship of the components in said blend is R152a/R600a:70/30. Utilization of isobutane possessing zero ozone depletion potential as a component of the 1,1-difluoroethane-based refrigerant blend, provides an appropriate zero value of this factor to the entire blend. Also, molecular mass of isobutane (58.12) is closer to the same factor of R152a (66.1), that of R22 (86.5). Therefore, a proportionality ratio defining an extent of fractionating the refrigerant blend component concentrations and equal to M 1 /M 2 , where M 1 and M 2 are molecular masses of the components, is 1.14 for the prior art refrigerant blend and 1.07 - for the blend according to the present invention. This, in its turn, reduces a probability of fractionating the components concentrations and, thus, reduces deviations over the optimal level of a refrigerator energy consumption. Estimations and tests revealed that within the proposed range of quantitative content of components according to the present invention, the refrigerant blend is an equal boiling mixture of azeotropic or close to azeotropic nature. This is particularly proved by the plots demonstrating the refrigerant blend pressure variation with R152a content. Brief Description of the Drawings Figure 2 is a plot of variation of a refrigerant blend pressure with R152a concentration at temperature 313.5 K. Figure 1 is a plot of variation of a refrigerant blend pressure with R152a concentration at temperature 353.15 K. The aforementioned advantages, as well as the features of the present invention are disclosed in the following description of the best mode of practicing the invention and are substantiated by estimated and test data of cycle refrigeration coefficient for the blend according to the present invention, as compared with R12 refrigeration coefficient. The Best Mode of Practicing the Invention Before filling up a refrigerator, a mixture of a predetermined quantitative content is prepared in a separate reservoir on the weight basis. To prepare 1 kg of the blend, 700 g of refrigerant (R152a) is poured to 300 g of isobutane (R600a) from a cylinder previously connected to a cylinder with isobutane. A refrigerator filling rate is defined on the basis of changing the weight of the cylinder containing P152a/P600a blend, which is connected to a suction pipe of the refrigerator compressor. For a refrigerator of "Birjusa-2" model, R152a/R600a filling rate is 80 g. The filling tube of a refrigeration unit is connected through a T-joint to the cylinder with the blend and to a vacuum pump. To remove foreign gases, the refrigeration unit should be pre-evacuated, a cylinder with the blend being closed at that time. After evacuation of foreign gases, the refrigerator is filled up with the blend at compressor actuated. The blend in a gaseous form is pumped into a refrigeration unit. The cylinder is located on a balance. After changing the weight of the cylinder by 80 g, the filling operation is terminated. The best filling rate for each refrigerator type is defined in view of a minimum daily energy consumption. Table 1 shows data for "Birjusa" refrigerator daily energy consumption when it operates on the refrigerant blend according to the present invention at concentration ratio R152a/R600a equal to 70 ÷ 30, and also when using R134a and R12 as refrigerants. Refrigerant Filling rate, g to in low-temp. heat exchanger °C to in high-temp. heat exchanger °C Daily energy consumption kW/h per day R134a 110 -18.1 +2.0 2.0 P12 120 -18.2 +2.3 1.8 R152a/R600a 80 -18.1 +2.2 1.75 From Table 1 follows that when using R12 and R134a as refrigerants, a refrigerator daily energy consumption is higher than the same when using 1,1-difluoroethane-based refrigerant blend according to the present invention. Table 2 depicts estimated and test data of a cycle refrigeration coefficient for R152a/R600a blend according to the present invention in comparison with R12 refrigeration coefficient. The latter has been chosen in view of substantial identity of its thermal characteristics to similar characteristics of R152a/R22 refrigerant blend, taken as a prototype, under an azeotropic relationship of components. Values of refrigeration coefficient E are given for t boil = 20°C, t cond = 55°C and temperature before a compressor t comp = 32°C. R152a/R600a, percent by mass Refrigeration coefficient E E <blend> to E <R12> ratio 50/50 0.846 0.99 55/45 0.852 0.99 60/40 0.858 1.00 65/35 0.861 1.01 70/30 0.861 1.01 75/25 0.857 1.01 80/20 0.847 0.99 R12 0.855 1.00 Table 3 shows data of heat measurements of a compressor of XKB model for three specific compositions of the refrigerant blend according to the present invention in comparison with R12, R152a and R600a refrigerants. Parameters R12 R152a R600a R152a/R600a 50/50 70/30 90/10 Evaporator pressure (P boil/atm ) 1.53 1.24 0.73 1.18 1.55 1.3 Condenser pressure (P cond/atm ) 14.5 13.7 7.85 13.8 14.6 14.4 Refriger. capacity (Q o /W) 173 145 84 148 180 153 Specific refriger. capacity 1.15 1.0 0.9 1.02 1.2 1.04 The tests were carried out under conditions similar to conditions of testing a refrigeration coefficient behavior. From Tables 2 and 3 is seen that within the ranges of R152a concentrations from 60 to 75 weight percent and R600a concentrations from 25 to 40 weight percent, the refrigeration coefficient is increased. Therefore, by adding isobutane to difluoroethane there is obtained a blend of two mutually soluble components having close molecular weights, possessing zero ozone depletion potential, the energy efficiency thereof being substantially equal to the same of R12 within a wide range of component concentrations. Moreover, the refrigerant blend within the concentration range according to the present invention has an azeotropic character and provides a refrigeration coefficient value exceeding that of R12 and of the prototype, respectively. Industrial Applicability A refrigerant blend according to the present invention can be utilized in medium-temperature refrigeration equipment and air conditioners, including vehicle and thermal pumps. Additionally, the blend can be used in existing refrigerators without essential structural modification thereof.

Claims: A 1,1-difluoroethane-based refrigerant blend comprising isobutane, characterised in that it comprises from 60 to 75 weight percent of 1,1-difluoroethane and from 25 to 40 weight percent of isobutane. The refrigerant blend according to claim 1, characterised in that it comprises 70 weight percent of 1,1-difluoroethane and 30 weight percent of isobutane.

Inventors: BARABANOV VALERY GEORGIEVICH, BELYAEV ANDREI JURIEVICH, CHIKUROV SERGEI KONSTANTINOVIC, EGOROV SERGEI DMITRIEVICH, KHMELNUK MICHAIL GEORGIEVICH, KONDRATIEV JURY ROALDOVICH, KOROTEEV ANATOLY SAZONOVICH, PONOMAREV-STEPNOI NIKOLAI NIKO, RUVINSKY GENRIKH YAKOVLEVICH, BARABANOV, VALERY GEORGIEVICH, BELYAEV, ANDREI JURIEVICH, CHIKUROV, SERGEI KONSTANTINOVICH, EGOROV, SERGEI DMITRIEVICH, KHMELNUK, MICHAIL GEORGIEVICH, KONDRATIEV, JURY ROALDOVICH, KOROTEEV, ANATOLY SAZONOVICH, PONOMAREV-STEPNOI, NIKOLAI NIKOLAEVICH, RUVINSKY, GENRIKH YAKOVLEVICH
Applicants: JOINT STOCK COMPANY INERTEK, JOINT STOCK COMPANY "INERTEK"
Application year: 1994
Main classification: C09K5
IPC codes: C09K5